With the development of communication technologies, it is important to ensure quality of data transmission. One aspect of ensuring data transmission quality is to detect a link fault quickly and locate the fault to facilitate maintenance of the link when the data transmission is faulty, for example, the voice of a call is not clear.
FIG. 1 shows a common composition of a link. As shown in FIG. 1, routers C, H, and E form a link. The routers C and E are end nodes (End Node, EN) of the link, and the router H is an intermediate node (Intermediate Node, IN) of the link. A data transmission process begins with sending data from a source end node, and ends with receiving all data correctly at the destination end node. In the data transmission process, when the user discovers quality deterioration of an end-to-end link between the router C and the router E, such as data delay or packet loss, it is necessary to determine whether the link quality deterioration is related to the router H.
To solve such a problem, the router H may ping C and ping E respectively. Ping is a technology of checking whether a channel or device is normal. The router H pings the node C, namely, the router H sends N ICMP (Internet Control Message Protocol, Internet Control Message Protocol) packets A. After the packets A arrive at the node C, the node C sends N packets A′ to the node H. The router H pings the node E, namely, the router H sends M ICMP packets B. After the packets B arrive at the node E, the node E sends M packets B′ to the node H, where N and M are natural numbers.
In the foregoing solution, the path followed by the packets of the two ping operations in the router H may be not completely the same as the path followed by the packets, which are forwarded by the router H and between the node C and the node E, in the router H. Therefore, the ping result is not enough for determining whether the link quality deterioration is related to the router H.